Employee Benefit Plans - Additional Information (Detail) (USD $)	6 Months Ended	3 Months Ended			3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Chesapeake Pension Plan [Member]	Dec. 31, 2012 Chesapeake Pension Plan [Member]	Jun. 30, 2013 FPU Pension Plan [Member]	Jun. 30, 2013 Chesapeake Pension SERP [Member]	Jun. 30, 2013 Chesapeake Pension SERP [Member]	Jun. 30, 2013 Chesapeake Postretirement Plan [Member]	Jun. 30, 2013 Chesapeake Postretirement Plan [Member]	Jun. 30, 2013 FPU Medical Plan [Member]	Jun. 30, 2013 FPU Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected pension and postretirement benefit costs	$ 999,000
Expected amortization of pre merger regulatory asset	769,000
Unamortized balance of regulatory asset		4,800,000	5,200,000
Contribution to pension plan	211,000	91,000			23,000	45,000	13,000	34,000	22,000	39,000
Additional contribution to pension plan		$ 364,000		$ 842,000	$ 88,000	$ 88,000	$ 97,000	$ 97,000	$ 258,000	$ 258,000